The present invention relates to a continuous-worm cigarette-making machine.
More in particular, the present invention relates to a conveyor system adapted to form a continuous layer of tobacco and to feed it to means for forming the so-called continuous cigarette worm.
Cigarette-making machines of the above described type are known which use a substantially vertical duct or chimney which is fed, at its lower end, with a continuous flow of tobacco particles and is upwardly closed by the lower stringer of an air-permeable conveyor belt closed in a loop around end rollers.
Inside the loop defined by said belt there is a chamber connected to a suction source and downwardly closed by a perforated plate; the lower stringer of the conveyor advances in contact with said plate.
Said plate constitutes a guiding and contrast element for said lower stringer, which extends in its direction of advancement beyond the outlet of the vertical chimney up to a position, termed discharge position, arranged at the intersection with the feeding path of a strip of cigarette paper.
The tobacco particles, pushed by a rising air current, rise through the vertical chimney and adhere to the lower stringer of the air-permeable belt due to the suction exerted by said chamber through the perforated wall and said belt, forming a substantially uniform layer of tobacco particles on said belt by accumulation.
This layer, still retained by suction by the conveyor belt, is transferred from the outlet of the vertical chimney to said discharge position, where it is deposited on the strip of cigarette paper.
The paper strip is then progressively closed on the tobacco layer so as to form the so-called continuous cigarette worm. The individual cigarettes are obtained from said worm by cutting.
In known cigarette-making machines, it has been observed that the use of the above mentioned perforated plate for the contrast and guiding of the lower stringer of the suction belt causes some disadvantages.
First of all, said plate reduces the suction force on said lower stringer intended to form and transfer the tobacco layer.
Tobacco dust furthermore penetrates and deposits itself between said lower belt stringer and the perforated plate and tends to obstruct the holes of said plate.
Finally, the high-speed flow of air through the holes of the plate causes a considerable increase in the noise of the machine.